Process of advancing heated yarn through free-running nip rolls under low tension



Nov. 19, 1968 5, CLAPSON 3,412,192

PROCESS OF ADVANCING HEATED YARN THROUGH FREE-RUNNING NIP ROLLS UNDER LOI TENSION Filed may 7, 1964 2 Sheets-Sheet 1 lrlvenlor B8144 Z'amea (Mme/v A "crazy;

Nov. 19, 1968 a. E. CLAPSON 3,412,192

PROCESS OF ADVANCING HEATED YARN THROUGH .PREE-RUNNING NIP ROLLS UNDER LOW TENSION Filed May '2. 1964 2 Shets-Sheet 2 In venlor Ee/m/ZZW/zea Attorney United States Patent 3,412,192 PROCESS OF ADVANCING HEATED YARN THROUGH FREE-RUNNING NIP ROLLS UNDER LOW TENSION Brian Edward Clapson, Cwmbran, England, assignor to British Nylon Spinners Limited, Pontypool, Monmouthshire, England Filed May 7, 1964, Ser. No. 365,743 Claims priority, application Great Britain, May 17, 1963, 19,677/63 5 Claims. (Cl. 264-290) ABSTRACT OF THE DISCLOSURE Yarn is heated, passed through the nip of a pair of freely-rotatable pressure rolls, and is wound up in the form of a package. One of the pressure rolls is gear-driven from a third roll which is driven by the forward movement of the yarn as it passes to the wind-up mechanism. This has the effect of reducing the tension in the yarn on the downstream side of the nip, thereby eliminating fraying or tearing of low-denier yarn.

The present invention concerns improvements in or relating to the treatment of yarns and filaments by pressure rolls.

It is known to pass yarns and filaments through the nip of cylindrical metal pressure rolls in order either to crimp them or to alter their filament cross-sectional shape or both. In certain processes the yarns or filaments are heated prior to passage through the nip, and in others they are rolled in the cold state. Two such processes for crimping are described in the specifications of our British patent specifications 936,284 and 913,882, respectively; and a process for crimping or deforming cold yarns and filaments is described in the specification of United States Patent No. 3,067,480.

It is often desirable to roll heated yarns in the course of another package-to-package process, such as a coming or re-winding process. There will then arise the difficulty of synchronising the roll speed with the machine wind-up speed, as for example that of the coming mechanism and to overcome such difliculty, recourse may be had to allowing the linear movement of the yarns or filaments to drive the rolls.

If such yarns or filaments are to be rolled so as to alter their filament cross-sectional shapes in a significant manner, in order that fabric woven or knitted therefrom shall be afforded a distinctively different handle and/ or appearance from that made from circular cross-section yarns or filaments of otherwise the same type, it is necessary not only that the yarns or filaments shall be heated, e.g. to 180-200 C. for polyhexamethylene adipamide yarns and filaments, but that they shall be pressed between the rolls whilst substantially twistless and at a high load.

Simply to draw heated yarns or filaments through the nip of a pair of loaded rolls and to drive them by such yarns or filaments andto be rolled under pressure by them, may indeed suffice for e.g. the heavier denier yarns or filaments; and such process is to be considered, therefore, to be the broadest aspect of the present invention.

Preferably, however, and particularly When the yarns or filaments are substantially twistless yarns of low denier, e.g. less than about 45 denier, and are thus likely to become frayed, weakened and even torn at the nip of the "ice rolls unless special precautions are taken, the process of the invention is modified by the provision of a further roll positioned downstream, for instance, of the pressure rolls and to one side of a line projected from the yarn path leading straight, i.e. tangentially, into the nip of said rolls, said third roll being driven by the yarn and itself driving one of the pressure rolls through gearing connecting it therewith.

The yarns or filaments are in that case threaded-up through the nip of the pressure rolls and around part, at least, of the periphery of the third roll which is driven by the forward movement of the yarns or filaments imparted thereto by e.g. the wind up mechanism, and such third roll itself drives one of the pressure rolls through gearing.

This latter arrangement of rolls and method of thread ing-up the yarns or filaments virtually eliminates any fraying or tearing of low denier yarns or filaments, because it reduces the tension in them on the downstream side of the nip. This is a result of the rotatable nature of the third roll and of its driving the one pressure roll, and also of the increased angle of contact of the yarns or filaments with that one pressure roll. Such increased angle of contact, alone, can be obtained by threading-up the yarns or filaments around such one pressure roll before passing them backwardly through the nip and thence around part of the periphery of the other pressure roll. Such a threading-up method, however, entails the loss of yarn heat prior to the pressure rolling, unless the pressure rolls are themselves heated; and naturally, as the extent of deformation of the filaments is dependent on their temperature at the time of rolling, any threading-up which involves the loss of heat previously imparted is not wholly to be recommended.

Again, the increased angle of contact as such can be obtained merely by deflecting the yarn path around a stationary guide member after rolling. In that case, however, the benefit of the increased angle is likely to be lost by reason of an increase both in wind-up tension and in tension immediately after emergence from the nip, the latter increase being chiefly responsible for the fraying or tearing effect on the yarns or filaments. Similarly, replacement of such stationary guide member merely by an idler roller to be driven by the yarn, but itself not driving the one pressure roll, does not overcome the latter tension increase.

Useful results in respect of the deforming of filament cross-section from circular to quasi-elliptical can be obtained by hot pressure-rolling substantially twistless polyhexamethylene adipamide yarns and filaments according to the invention, so that the mean aspect ratio of their filaments lies between about 1.2 and 1.4. Below 1.2, the effects are not sufficiently noticeable, whereas above 1.4 the filaments are becoming too weakened for many purposes. By mean aspect ratio is meant the mean ratio of the longest axis of symmetry divided by the shortest axis of symmetry. As a result, the opacity of the yarns is increased, and a drier handle is imparted to fabrics woven from them than is possessed by similar fabrics woven from circular cross-section filamentary yarns. Furthermore, owing to the random nature of variations in the cross-sectional shape of the filaments along their lengths, the appearance of the fabric is altered in a way that can be quite desirable, being the novelty effect known as crackiness, i.e. having randomly distributed short lines of a darker nature interspersed between the areas of regular nature, in the Warp and/ or weft directions of a woven fabric.

Apart from use in woven fabrics, such twistless yarns pressure-rolled according to the invention may be used in the welts of stockings; and then the pressure-rolling can be carried out as an intermediary step of the coning process, before being wound-up by the coning mechanism.

It is possible to roll a plurality of yarns or filaments at one time between a single pair of pressure rolls, but in that event, for uniformity of treatment, care must be taken to ensure that the pressure along the line of the nip is uniform. It may be necessary, therefore, to back the nip rolls with larger rolls as described in US. patent specification No. 3,067,480.

The invention will now be described with reference to the accompanying drawings, in which FIGURE 1 is a general arrangement diagram illustrating the process of the invention:

FIGURE 2 is a perspective view of a yarn heater and of a preferred embodiment of apparatus according to the invention;

FIGURE 3 is a diagram of an alternative threading-up in apparatus according to the invention;

FIGURE 4 is a diagram of a further alternative threading-up in apparatus according to the invention.

In FIGURE 1, yarn Y is withdrawn over the top end of supply bobbin 1, by virtue of the winding action of a ring-spindle wind-up comprising rotating spindle 3, traversing ring 5, traveller 7, wind-up bobbin 9 and balloon guide 11.

The yarn Y passes upwardly through guide 13 and thence around the periphery of tension-imparting means 15, which imparts a low tension to the yarn.

Thence the yarn is drawn in contact with the upper convex shaped surface of heater plate 17, which is electrically heated by an internal resistance supplied via electric leads 19.

Immediately beyond the downstream end of the heater plate, the yarn is drawn through the nip of freely-rotatable pressure rolls 21, 23, and wrapped partly around the periphery of roll 23 before being changed in direction around a portion of the periphery of a third freely-rtatable roll 25. Rolls 23 and 25 are interconnected by gearing 27. The yarns direction is again altered, downwardly, through guide 29.

The forward motion of the yarn in contact with the periphery of roll 25 imparts rotary motion to it, which in turn is transmitted via the gearing to roll 23. Hence, the forward motion of the yarn is responsible for driving the rolls 21, 23, as the rotary motion of roll 23 is imparted directly to roll 21 by contact of their peripheries through the yarn moving therebetween.

In FIGURE 2, the embodiment of the apparatus, as shown more diagrammatically in FIGURE 1, consists of roll 21 fixedly mounted on freely-rotatable shaft 22, roll 23 fixedly mounted on freely-rotatable shaft 24, and roll 25 fixedly mounted on freely-rotatable shaft 26. Shafts 24 and 26 are interconnected by gearing 27. Not shown in this drawing are the means whereby roll 23 is loaded to press its periphery against that of roll 21. Such means may be of the type described and illustrated in the specification and drawings of the aforementioned British patent specification 936,284. Heater plate 17 is mounted upstream of the rolling mill apparatus.

In FIGURE 3, a threading-up of the yarn in a manner that will drive the pressure rolls is shown which requires no other means. The yarn is passed around the underside of roll 21, thence backwardly through the nip between rolls 21 and 23, and then around the upper side of roll 23.

In FIGURE 4, a threading-up employing a freely-rotatable roller or stationary pin 28 downstream of pressure rolls 21 and 23 is shown. In this case, the yarn passes directly from the heater 17 into the nip of the rolls 21, 23, thence around a portion of the periphery of roll 23 before being turned in direction around roller or pin 28.

In the following examples of the invention, the yarns were rolled singly in a process such as that illustrated in FIGURE 1. The yarns were of polyhexamethylene adipamide, and contained only such small amount of twist, e.g. of /2 turn per inch, as is customarily inserted by the manufacturer at the completion of the drawing process.

In the first case, the yarn of denier/68 filaments was withdrawn at 100 feet/ minute from its supply package by rotation of a take-up bobbin, and a tension of 1 gram was applied by a tensioning device positioned immediately upstream of a contact heater plate. The yarn was passed in contact with the heater plate, which was electrically heated just above C., and then immediately passed between the nip of stainless steel pressure rolls to which a load of 68 pounds was applied. The yarn was deflected from its straight line path to pass partly around and to drive a third (unloaded) stainless steel roll, whose rotational movement was geared to drive the upper one of the pressure rolls. The yarn was then wound up on the bobbin at a low tension.

In the second case, the process was similar but the supply yarn was of 45 denier/ 15 filaments, and the speed of rolling was 500 feet/minute. The tension applied was 3 grams, and the temperature of the yarn at rolling was 200 C. The load applied was 68 pounds, as before; and it resulted in a mean aspect ratio of the filaments of 1.25.

In both cases, fabric woven from the respective yarns in both warp and weft had a drier, soften handle and better covering power (i.e. greater opacity) than control fabrics woven from yarns that were otherwise similar, but had circular cross-section filaments.

I claim:

1. A process for treating yarns and filaments comprising the steps of (a) advancing the yarn or filament to cause it to travel towards wind-up means;

(b) imparting a low tension to said travelling yarn or filament;

(c) heating said tensioned, travelling yarn or filament;

((1) immediately thereafter subjecting said heated yarn or filament to pressure between the nip of loaded pressure rolls; and

(e) imparting rotary motion to said pressure rolls solely by the forward movement of said yarn or filament via gearing from a third roll which is itself driven by the forward movement of said yarn or filament.

2. A process according to claim 1, in which said third roll is positioned downstream of said pressure rolls and to one side of a line projected from the yarn path leading tangentially into the nip of said rolls.

3. A process as in claim 1 wherein the yarn is substantially twistless multifilament yarn of polyhexamethylene adipamide and wherein said heating step heats said yarn to a temperature between 180 C. and 200 C.

4. A process according to claim 3 in which the crosssections of the individual filaments are deformed by the pressure rolls to the extent that the mean aspect ratios of the filaments lie between 1.2 and 1.4, and their crosssection varies randomly along the lengths.

5. A process for treating yarn of denier below about 45 and winding the yarn into a package which comprises: advancing the yarn by a wind-up means; imparting a low tension to the travelling yarn; heating the tensioned, travelling yarn; immediately thereafter passing the heated yarn through the nip of freely-rotatable pressure rolls; eliminating fraying or tearing of the yarn by driving a nonpressure roll through engagement of the travelling yarn with the periphery of said non-pressure roll and by mechanically driving one of said pressure rolls from said non-pressure roll; and winding up the yarn without further treatment thereof with pressure rolls.

(References on following page) 5 6 References Cited FOREIGN PATENTS UNITED STATES PATENTS 1,350,801 12/1963 France. 2,738,144 3/1956 Honig 242 151 913,882 12/1962 G e B m- 2,932,077 4/1960 Honig 242155 5 JULIUS FROME, Primary Examiner.

3,196,602 7/1965 Jenkins et a1. 2872 A. KOECKERT, Assistant Examiner. 

